[5] Since her introduction in comics, the character has been featured in various other Marvel-licensed products, including video games, animated television series, and merchandise.

[15] Through the actions of her son Nicholas Scratch, she was revealed as a member of the previously unknown New Salem, Colorado, a colony of witches of whom she had been the leader.

In an ensuing battle between the Scarlet Witch and Salem's Seven, the entire community's energies were drawn into Vertigo of the Seven, who lost control of them.

Following hints from Agatha's astral form, Wanda channeled the remaining energy to become pregnant with twin children of Vision, her android husband.

[27] Agatha fights alongside Wanda and the spirit of her biological mother Natalya Maximoff against a physical manifestation of Chaos which is attempting to destroy witchcraft.

The two spirits channel their magic through Wanda and, after Quicksilver is summoned, they manage to defeat the being once and for all although this has gravely wounded Order, the Goddess of Witchcraft.

At the time when Captain America figured out that Dryad is a revived Peggy Carter, Agatha teleported herself to inform him that the threats that the Daughters of Liberty have been facing are connected with Aleksander Lukin's sister Alexa.

[29] Agatha later briefed the Daughters of Liberty's latest recruit Shuri about the situation involving Selene having Sharon Carter's soul.

The two exchange some small talk before Agatha brings up the topic of Chthon (which was sealed inside her soul) and the Darkhold (which Wanda had absorbed).

Scarlet Witch thinks she's strong enough to take on this burden, while Agatha believes otherwise as she has become aware of several threats looming in the shadows looking to take advantage of Wanda.

However, part of Agatha Harkness' fight against the Scarlet Witch was secretly about gaining access to the Darkhold trapped in Wanda Maximoff's soul.

[32] During the "Contest of Chaos" storyline, Agatha uses Chthon's remains to create a new Darkhold and starts by having Spider-Man and Wolverine fight each other in the Amazon rainforest.

After a brief battle with Clea on the Astral Plane, Agatha returns to her body in the Bermuda Triangle while in the presence of her champions.

[40] During the "Blood Hunt" storyline, Agatha and the Darkhold's human form are traveling on a train incognito as they are being pursued by Scarlet Witch.

[43] Harkness can manipulate magical forces for numerous effects by invoking beings or objects existing in vast dimensions tangential to Earth through spell recitations, such as psychokinesis, levitation, and the tapping of extra-dimensional energy.

[29] Deirdre Kaye of Scary Mommy called Agatha Harkness a "role model" and a "truly heroic" female character.

He praised Kathryn Hahn's portrayal of Harkness, describing her as a "legendary character actress" who transformed what could have been a forgettable villain into a standout performance in the MCU.

[54] Ben Saffle of Comic Book Resources stated Harkness gained a "fandom following her antics" in WandaVision which resulted in her starring in her own spin-off.

[55] Richard Fink of MovieWeb said that Hahn’s portrayal of Harkness in WandaVision transformed her from a quippy villain into a standout character within the MCU.

Fink found that Harkness' journey from antagonist to potential ally creates opportunities for compelling storytelling in her own television series.

He stated that Harkness could fill a similar role to Loki as a charismatic villain, adding depth to the MCU's expanding mystical universe.

[58] In the Old Man Logan reality of Earth-21923, Agatha Harkness was shown to be in a village somewhere in the Presidential Quarter having her powers siphoned by Baron Mordo.